The present invention relates to vibratory feeders and particularly to a vibratory feeder for conveying materials, which has a self-contained power control circuit.
Vibratory feeders have been widely used in controlling the bulk delivery of various types of product including materials for use in feeding, mixing, grinding and packaging. Generally, the vibratory feeders are comprised of two elements, commonly referred to as two masses, which are vibrated with respect to one another. The first element is generally referred to as a base, and the second element is generally referred to as a trough. Located between the two elements is a vibratory drive, which vibrates the trough with respect to the base. As the trough is vibrated with respect to the base, the material located in the trough is conveyed or thrown forward at a predetermined rate, the rate being determined by the frequency, the force, and the angle of the vibrations.
The trough, is generally disposed above the base and is connected to the base by a system of springs. The springs are connected to the trough and base on an angle. A vibratory drive is mounted to the base and operatively coupled to the trough, so as to impart vibrations to the trough with respect to the base. At least one example of a vibratory drive includes an armature of an electromagnet, which is connected to one of the base or trough, usually the trough, and an electromagnet core and coil, which is connected to the other.
The feeder as a whole, generally rests upon a support structure. The base of the feeder, while resting upon the support structure, is generally vibrationally isolated from the support structure by one or more coil springs, or elastomer springs to minimize unwanted forces from being transmitted into the support, and surrounding structures.
When an electric current is caused to flow through the magnet, the armature and magnet pole faces are mutually attracted to each other, causing the springs to deflect, and the trough to be displaced with respect to the base, and relative to their rest positions. When the current is removed, the magnet releases the armature and the energy stored in the spring system causes the trough to move back toward its rest position. The movement of the trough generally continues through the rest position to a deflected position in the opposite direction, where the movement of the trough with respect to the base once again changes direction, back toward the rest position. As current is reapplied and removed, the process is repeated. If the current is turned on and off at a uniform rate, the trough and base will generally vibrate with respect to one another at a similar rate, or frequency.
In at least one type of vibratory feeder, the vibratory feeders are operated at a frequency determined by the power line frequency, or at twice the power line frequency where a diode rectifier is used, or a permanent magnet is used as part of the electromagnetic vibratory drive system. Examples of such feeders are manufactured by FMC Corporation of Homer City, Pa., under the trade name SYNTRON. In such feeders, the frequency is fixed at 120 Hz or 60 Hz in North America, and 100 Hz or 50 Hz (usually 50 Hz) in most other countries of Europe or Asia. Since the frequency at which these feeders operate is generally fixed, only the stroke and stroke angle can typically be adjusted to optimize the feed rate. The stroke angle is largely dependent upon the construction and the orientation of the parts with respect to one another. Once the specific construction of the vibratory feeder has been determined, the stroke angle for that particular model becomes relatively fixed. Consequently, only the stroke magnitude remains as a parameter, which can be adjusted for adjusting the feeder""s performance. Even still, the stroke magnitude of these feeders is constrained by the amount of magnetic force available to deflect the spring system, and ultimately by the stress limitations of the spring system and the other structural elements of the feeder.
The vibrational feeders generally attempt to take advantage of the natural amplification of the stroke due to resonance, by adjusting the natural frequency of the mass/spring system to be close to that of the operating frequency. This assures that there will be sufficient power available to operate the feeder with a reasonably sized electromagnetic. A typical maximum stroke value for feeders, of the above mentioned type, operating between 50 and 60 Hz. is between approximately 0.0625 inches and approximately 0.144 inches. Generally the lower the frequency the greater the possible maximum value of the stroke. A more detailed discussion of stroke angle and stroke magnitude is discussed in connection with Patterson et al., U.S. Pat. No. 5,967,294, entitled xe2x80x9cHigh Stroke, Highly Damped Spring System for Use with Vibratory Feeders, the disclosure of which is incorporated herein by reference.
As the vibratory drive is actuated, and the trough is accelerated, the material resting on the surface of the trough is accelerated with the trough. As the trough reaches its maximum point of deflection, the trough begins to slow down and move back. If the material located in the trough has been accelerated sufficiently for the material to take flight, the material will continue to move forward as the trough reaches its maximum deflection, changes direction and moves back toward its rest position. Eventually, the material will fall back toward the surface of the trough, generally displaced at some distance forward from where the material originally took flight. During subsequent applied vibrations, the material is progressively moved even further forward. In this way, the material located in the trough can be conveyed in the desired direction by the vibratory feeder.
Generally, the magnitude and the frequency of the vibrational force applied to the trough is controlled by the characteristics of the power signal supplied to the vibratory drive of the vibratory feeder. In current vibratory feeders the power signal supplied to the vibratory feeder is generally controlled by an external controller. The external controller generates a conditioned power signal having the specific magnitude and frequency necessary to convey the material located in the trough at the desired rate and in the appropriate direction. The conditioned power signal is then conveyed over power lines specific to the corresponding vibratory feeder. Often times the external controller has one or more controls for adjusting the characteristics of the power that is supplied to the vibratory feeder.
Individual control of the specific power characteristics supplied to each vibratory conveyor is important, because each vibratory feeder will have its own unique material conveyance characteristics including its own resonant frequency. The material conveyance characteristics will vary between different vibratory feeders, due to inherent differences, which can result from known tolerances during their manufacture and/or dissimilar wear during their subsequent use. Where multiple vibratory feeders are used within the same system for a particular process it will likely be necessary to separately adjust each of the individual vibratory feeders in order to correctly manage material flow. As a result, each feeder will have a different power requirement, regardless of whether or not the material conveyance rates are the same or different for the different vibratory feeders. Consequently, prior systems have traditionally run separate power lines to each vibratory feeder, even where the multiple vibratory feeders are controlled through a common external controller.
As noted previously, vibratory feeders are commonly used in controlling the bulk delivery of product. One such noted example includes the use of vibratory feeders in product packaging. In many such instances multiple vibratory feeders are needed to provide accurate weights and corresponding processing rates demanded by the packaging process. Often times the multiple vibratory feeders are aligned either linearly or peripherally about a processing head for access by a packaging machine. Because each vibratory feeder has its own power requirements, each vibratory feeder will have its own corresponding power lines. Unfortunately, the physical routing requirements for running separate wiring for each vibratory feeder in a system where multiple vibratory feeders are used can be quite burdensome. Furthermore, because the power signals being supplied to vibratory feeders generally have a signal amplitude of a hundred volts or more, electrical cross-talk and interference between different sets of power control lines can be a problem, especially where the vibratory feeders and the separate corresponding sets of power lines are located proximate to one another.
Consequently, it would be desirable to provide a vibratory feeder, which is capable of locally providing for any required power adjustments, thereby enabling multiple vibratory feeders to receive power from a shared set of power lines.
These and other objects, features, and advantages of this invention are evident from the following description of a preferred embodiment of this invention, with reference to the accompanying drawings.
The present invention provides for a vibratory conveyor which includes a base and a trough. The vibratory driver is mounted to said base and is operatively connected to the trough to impart vibrations thereto. An integrated power control circuit is connected to the vibratory drive and a common supply bus for generating a locally adjusted drive signal. the locally adjusted drive signal is then supplied to the vibratory drive. In a preferred embodiment the power control circuit includes an output rate adjustment, which controls at least one of a frequency and an amplitude of the adjusted drive signal.
By incorporating a power control circuit as part of each vibratory conveyor, the one or more vibratory conveyors can receive power from a common or shared set of power lines. Any required adjustment of the power signal is provided locally by the power control circuit integrated as part of the vibratory conveyor. In this way it is no longer necessary to run separate power signals along separate power lines to each vibratory conveyor. The specific power adjustment (i.e. power shaping) for each vibratory conveyor is performed locally. This allows for specific power adjustments to similarly follow the vibratory conveyor, if the vibratory conveyor is subsequently moved. As a result initial setup or subsequent reconfiguration of the vibratory conveyors can be accomplished without requiring the routing or reconfiguration of separate power lines.
To the extent that it may be desirable to continue to route specific control signals to a vibratory conveyor, this can be accomplished using control signals having lower and safer voltage levels. Furthermore the signals could be digitally encoded and/or superimposed upon the power signals being routed along the common supply bus.
Other features and advantages of the present invention will be apparent from the following detailed description, the accompanying drawings, and the appended claims.